Known bag assemblies formed of a blown film of plastic material include provisions for bonding using a thin layer of a contact adhesive material whereby folds and common bonding are effected after evaportaion of solvent from the adhesive material. Accordingly, the adhesive is applied in layers in an almost dry condition and bonds only to itself, e.g. adhesive layer to layer bonding.
Thus, tubularly-shaped bag preforms, formed for example by blown film techniques, are passed through the bag forming assembly in a manner to minimize contact between adhesive layers, end forming tools, guide bars and the like. However, it has been found that orifices and/or channels are formed between folds during processing of the preforms as a result of inherent resiliency of the plastic material forming the preforms, particularly when forming forces are inadequate to effectively contact adhesive layers to close corner folds, side folds, end folds, etc. thereby resulting in potential subsequent leakage of a packaged product therefrom.
Inadequate contact, and thus potential product leakage, occur as a result of using cover sheets in known assemblies, where the cover sheets are of a thickness greater than the thickness of the bag preform or of common overlapping folds at certain areas of the bottom end closure, since breakage of such cover sheets along a longitudinal direction may readily occur along an edge of side bottom folds by impact-like stresses.